The ads were pervasive, popping up on CNN, Fox News, NPR, and Google searches. And they were persuasive: Playing Lumosity games would do your brain good.

“Can you remember the name of that song you just heard?” one announcer asked Pandora listeners. “Most people find that memory declines with age. But your memory doesn’t have to. Control and improve your memory with Lumosity.com, the personal trainer for your brain.”